1. Field of the Disclosure
The disclosure relates to computer data input, and more specifically, to a method and system of data input for an electronic device equipped with a touch screen.
2. Description of the Related Art
With recent innovations in functionality and application development, touch screens are experiencing a dramatic surge in popularity for electronic device input.
Compared to conventional input, such as a keyboard and/or a pointing device, touch screens provide a considerable improvement in convenience; no external devices or bulky real-estate-hogging components are required, since the screen can mimic the functionality of a keyboard via software when desired, and positions can be indicated directly on the screen via touch rather than indirectly chosen by using a separate mouse (or joystick, eraserhead, touchpad, or other controller) to move a virtual cursor. However, touch screens register input from simple screen surface contact or capacitive flux sensing only, with variations in input detection generally limited to initial contact and sliding contact. Capacitive sensing devices are of low resolution, prone to noisy signals, and at the hardware level report a matrix of sensed capacitances; the hardware then processes the matrix to filter out the noise, finally sending a touch event, containing the center and size, for each pattern that exceeds an arbitrarily chosen threshold. Because of the noisy signal, touch events are generated only for large patterns. The threshold is usually chosen to find touches that are from a fingertip-sized touch, for example 10 mm in diameter. Furthermore, the means of initiating the contact, such as by fingertip, by stylus, or by other means, cannot be determined; for example, using a touchscreen outdoors during a rainstorm can result in random “touches” from large-enough raindrops or the puddles they form. Lastly, capacitive touch screens do not actually detect contact, they detect the capacitance of any large-enough conductive objects that are near the screen; bringing a finger close to a touchscreen can generate an event even when the user is hesitating about, for example, clicking on a “buy it now” button.
Hardware solutions raise the cost of devices. High-resolution touchscreens are available, but are expensive; raising the gain of lower-resolution capacitive sensing devices increases noise and hence false detection of contacts, in addition to draining batteries much more quickly.
As a consequence, users are forced to use awkward holding methods to avoid inadvertent contact with the touchscreen that would otherwise result in unwanted input, or else the users must deal with unwanted input that occurs from touching the touchscreen with their palms and fingers. Unlike writing on a pad of paper, where the user typically rests his palm against the pad, on a touchscreen the user must keep his hand away from the screen.
The rejection of unwanted input is sometimes referred to as the “palm rejection” problem, where resting the palm of the hand on the touchscreen or gripping the touchscreen device with fingers touching the touchscreen, while using a finger or a stylus to generate a desired input, causes the device also to register inadvertent undesired input from the hand contact. One solution would be to require the use of a special input tool at all times, but this lacks flexibility and impairs convenience for the user, and may increase manufacturing costs in order to create touchscreen hardware that would detect the difference between the tool's touch and a finger/palm/other non-tool touch. Moreover, not all such contacts are unwanted; a user may choose to switch between the use of a stylus for precision and a finger for convenience, even while using the same application, for example when switching between drawing a sketch (stylus) and touching menu controls (finger); and yet a user may need to stabilize a hand against the device touchscreen, for example when in a moving vehicle on a bumpy road, in order to use a stylus with sufficient precision to generate desired input, for example when using a stylus to select a position for input into a map application. Because of these conflicting user needs, the problem of palm rejection is a difficult one.
Thus, what is called for is a method and system of data input for an electronic device equipped with a touch screen addressing the limitations described.